With the rapid development of science and technology and the popularization of automation technology, customers are increasingly demanding materials testing machines, especially in terms of test accuracy, real-time display, and data processing. This means that our manufacturers must promptly upgrade the test machines that cannot keep pace with automation, so that they can demonstrate the most powerful functions in this high-tech era.
The disadvantages of the original electro-hydraulic servo puller:
(1) The application of single-chip microcomputer system to transform universal material testing machine, its main advantages are the simple structure, small size, low cost, easy to implement the embedded system. But the circuit system is complicated, the stability of the system is not high, the data processing speed is slow, and real-time control cannot be realized. The key problem in the field of testing machines today is that a constant stress rate or a constant strain rate must be maintained during loading. Obviously this effect cannot be achieved with this method.
(2) The use of a speed controller to control the motor to control the pressure application load and speed current feedback is a traditional control method. For example, the position controller is used to calculate the number of stepper motor drive steps to obtain good stress rate, strain rate, displacement rate control, and test results for constant load, constant strain, and displacement control. However, the hydraulic universal material testing machine is a typical non-linear time-varying system. It is difficult to establish an accurate mathematical model. It is difficult to achieve the ideal control effect by using a conventional controller. In the actual scene, due to the complexity of parameter tuning methods, the application of conventional controllers is often poorly tuned, poor performance, and poor adaptability to operating conditions.
(3) The use of computer and sensor technology for the transformation of old-style material testing machines and monitoring equipment, the use of electro-hydraulic proportional valves or electro-hydraulic servo valves to achieve high-precision control of the stress and strain rate control problems, measurement and control systems using computer cards Design, using opto-isolated integrated circuits. With the advantages of strong anti-interference ability, reliable quality and high stability, it can be completed with a click of a mouse and is easy to use. Can also draw a variety of test curves, with curve data storage and curve amplification function, suitable for testing machine to a high degree of automation, easy operation, high reliability, good stability direction of development. Which transformation program to choose, combined with the actual situation, choose the best transformation program to meet the needs of users. Considering comprehensively, we use the third option, that is, installing load, deformation and displacement sensors on the hydraulic universal testing machine, increasing the loading speed of the electro-hydraulic valve, and upgrading the equipment from the original traditional mechanical load measurement system to the more advanced electronic measurement. Force, measuring deformation system
Mechanical parts and hardware components
In addition to the original manual loading part, the system was rebuilt, another branch was added, and the electro-hydraulic proportional valve was used to control the loading rate of the testing machine. This allows both manual and automatic control. A high-precision pressure sensor is added at the inlet pipe to measure the pressure of the system, and displacement measurement systems and computer acquisition and processing technologies are used to automatically collect, analyze, and process the data. In data collection, the collection speed is fast and the measurement accuracy is high. In data analysis, consideration is more comprehensive; in data processing, it has the features of intelligent interaction, illustration and text, and can be represented in various ways such as numerical display, charts, and curves. Data, and various analysis and processing of experimental data according to teaching requirements. Let the testing machine in the signal detection, data processing is closer to the development level of modern testing machine, to adapt to the current development of testing machines at home and abroad for intelligent, accurate, easy to operate, stable and reliable development trend.
Therefore, the upgraded electro-hydraulic servo tensioner consists of the following major components.
(1) The host part. Mainly consists of cylinder, working piston, base, worktable, column, moving beam up and down, sample clamp and movable beam, etc. The main function is to clamp and fix the sample by the sample holding mechanism,
load.
(2) Hydraulic control section. Mainly consists of fuel tank, high pressure oil pump, delivery valve, oil return valve, electro-hydraulic proportional valve, stop valve, force measuring cylinder piston, main engine working oil cylinder, working piston, etc. The main function is to control the clamping and test piece of the test piece. The loading.
(3) Detection section. Mainly by the load sensor (pressure sensor), electronic extensometer, photoelectric encoder (displacement sensor) and other components, the main function is to test the test subject by the test force, deformation and displacement of the beam movement.
(4) data acquisition processing and control part. Mainly consists of data acquisition, processing, control circuits, computer hardware and software systems, printers, manual control devices, etc. The main function is to complete the control of the entire system, the setting of various parameters, display, test procedures and test results, test data Processing, storage, and output of test results.
(5) Electrical section. The basic components of the relay include various types of relays, AC contactors, and switch buttons. The main functions are the switch of the oil pump motor, the control of the movement of the crosshead lifting mechanism, and various limit and overload protections.
(6) Attachments. Mainly by the tensile, compression test fixture, bending test accessories and other special test accessories (various plug, chuck) and other components. Its basic function is to complete various specific tests by replacing the fixture.
The structural design of the control software of the electro-hydraulic servo tensioner software directly influences the ease of operation and the reliability of the data, and even affects the successful transformation. The test software consists of five modules: data acquisition, graphic output, data output, report printing, and proportional control (servo control).
1 The main function of the data acquisition module is to set the initialization parameters, such as the acquisition time interval, the total acquisition time, etc., as well as sensor zero adjustment, calibration, etc.;
2 graphics output module means that in the collection process, according to the graphics drawn by the data is output to the screen, or after processing the data graphics output from the printer;
3 The data output module is mainly to print the key point data of the material performance and the data in the collected data for a certain period of time from the printer, or manually modify, increase or decrease certain data and save it;
4 report printing module refers to the experiment is done, the key performance data of the material, the original graphics in a fixed format of the experimental report printout;
5 Proportional servo control module is mainly to control the proportional pressure flow compound valve, including the initialization and setting of the D/A card.
The function and conclusion of the reform of electro-hydraulic servo tension machine
(1) The advanced digital proportional pressure flow compound valve is used as a control element to realize the microcomputer automatic control of the loading force value and loading speed. With load force controllable, low speed and high load test effect, stable and reliable test performance
specialty.
(2) Computer screen display data, including deformation, loading rate, deformation rate, material characteristics (upper and lower yield point, maximum point, fracture point), elastic modulus, area shrinkage, etc. Experimental results can be organized into a report, convenient and intuitive Good real-time performance.
(3) Support the printer and plotter to print the experimental results and draw the experimental curves. The screen is what the report sees. It can print and store batches of experimental reports and inspection reports, and retain the experimental report permanently. [7]
(4) The original manual loading part is preserved during the transformation, so that it can be manually operated and can be automatically controlled, which is convenient and flexible and beneficial to teaching. The key to the success of the test machine transformation is to see if the accuracy of the final test data meets the requirements and whether the test curve is drawn accurately. After the transformation, it was verified through specific data and graphs that the transformation was successful. It was more accurate and reliable than ever before, whether it was from the test accuracy or the test method.
